Answer:
(300 + 50x)/(2 + x)
Explanation:
Let the cost of teachers' edition books be t
Let the cost of students' edition books be s
So t = 150; s = 50
Then the total cost of 2 teachers' editions and x students' editions is 2t + sx = 2 × 150 + 50x = 300 + 50x.
The total number of books is 2 + x.
So the average cost per book is (300 + 50x)/(2 + x)